Peter O’Brien, 1st and last Baron O’Brien1 
He was Privy Counsellor (P.C.)2 He was Doctor of Law (LL.D.)2 He graduated from Trinity College, Dublin University, Dublin, County Dublin, IrelandG, with a Master of Arts (M.A.)1 He was admitted to King’s Inn in 1865 entitled to practise as a Barrister-at-Law.1 He was appointed Queen’s Counsel (Q.C.) in 1880.1 He was senior Crown prosecutor in 1883 at Dublin, County Dublin, IrelandG. He was a practising Serjeant-at-Law in 1884.1 He held the office of Bencher of King’s Inn, Dublin in 1884.1 He held the office of Solicitor-General [Ireland] between 1887 and 1888.1 He held the office of Attorney-General [Ireland] between 1888 and 1889.1 He held the office of Lord Chief Justice [Ireland] in 1889.1 He was created 1st Baronet O’Brien [U.K.] on 28 September 1891.1 He was created 1st Baron O’Brien, of Kilfenora, co. Clare [U.K.] on 16 June 1900.1
Children of Peter O’Brien, 1st and last Baron O’Brien and Annie Clarke
- James O’Brien1
- Annie Georgina O’Brien1
- Hon. Ellen Mary O’Brien1 d. 13 Oct 1930
- [S21] L. G. Pine, The New Extinct Peerage 1884-1971: Containing Extinct, Abeyant, Dormant and Suspended Peerages With Genealogies and Arms (London, U.K.: Heraldry Today, 1972), page 210. Hereinafter cited as The New Extinct Peerage.
- [S47] BIFR1976 page 241. See link for full details for this source. Hereinafter cited as. [S47]
John O’Brien1 
He held the office of High Sheriff of County Clare in 1836.1 He held the office of Member of Parliament (M.P.) for the City of Limerick between 1841 and 1852.1 He lived at Elmvale, County Clare, IrelandG.1 He lived at Ballynalacken, County Clare, IrelandG.1
Children of John O’Brien and Ellen Murphy
- John O’Brien1 d. 1889
- William O’Brien1
- Terence O’Brien1
- Margaret O’Brien1
- Ellen O’Brien1
- Catto O’Brien1
- Anne O’Brien1
- James O’Brien1 b. 9 Jan 1832
- Jerome O’Brien1 b. 1835, d. 1892
- Peter O’Brien, 1st and last Baron O’Brien+1 b. 29 Jun 1842, d. 7 Sep 1914
- [S21] L. G. Pine, The New Extinct Peerage 1884-1971: Containing Extinct, Abeyant, Dormant and Suspended Peerages With Genealogies and Arms (London, U.K.: Heraldry Today, 1972), page 210. Hereinafter cited as The New Extinct Peerage.
- [S142] Bernard, Sir Burke, editor, Burke’s genealogical and heraldic history of the landed gentry of Ireland, 3rd ed. (London, U.K.: Burkes Peerage Ltd, 1912), page 519. Hereinafter cited as Landed Gentry of Ireland.
James O’Brien1 
He lived at Limerick, County Limerick, IrelandG.1 He lived at Elmvale, County Clare, IrelandG.1
Children of James O’Brien and Margaret Long
- John O’Brien+1 b. 6 Dec 1794, d. 6 Feb 1855
- Peter O’Brien1 b. Sep 1797, d. 1855
- Terence O’Brien1 b. 1802, d. 1820
- James O’Brien1 b. 1806, d. 1882
Torlogh O’Brien1
He lived at Elmvale, County Clare, IrelandG.2 He was also known as Terence O’Brien.2
Children of Torlogh O’Brien and Eleanor O’Hogan
- James O’Brien+1 d. 21 Feb 1806
- John O’Brien2
Torlogh O’Brien1
He was also known as Terence O’Brien.2
Child of Torlogh O’Brien and Elizabeth O’Brien
Elizabeth O’Brien1
Child of Elizabeth O’Brien and Torlogh O’Brien
- [S21] L. G. Pine, The New Extinct Peerage 1884-1971: Containing Extinct, Abeyant, Dormant and Suspended Peerages With Genealogies and Arms (London, U.K.: Heraldry Today, 1972), page 209. Hereinafter cited as The New Extinct Peerage.
Henry O’Brien1
Child of Henry O’Brien
- [S21] L. G. Pine, The New Extinct Peerage 1884-1971: Containing Extinct, Abeyant, Dormant and Suspended Peerages With Genealogies and Arms (London, U.K.: Heraldry Today, 1972), page 209. Hereinafter cited as The New Extinct Peerage.
Eleanor O’Hogan1
Her married name became O’Brien.1
Children of Eleanor O’Hogan and Torlogh O’Brien
- James O’Brien+1 d. 21 Feb 1806
- John O’Brien1
- [S21] L. G. Pine, The New Extinct Peerage 1884-1971: Containing Extinct, Abeyant, Dormant and Suspended Peerages With Genealogies and Arms (London, U.K.: Heraldry Today, 1972), page 209. Hereinafter cited as The New Extinct Peerage.
Mortogh O’Hogan1
Child of Mortogh O’Hogan
- [S21] L. G. Pine, The New Extinct Peerage 1884-1971: Containing Extinct, Abeyant, Dormant and Suspended Peerages With Genealogies and Arms (London, U.K.: Heraldry Today, 1972), page 209. Hereinafter cited as The New Extinct Peerage.
John O’Brien1 
- [S21] L. G. Pine, The New Extinct Peerage 1884-1971: Containing Extinct, Abeyant, Dormant and Suspended Peerages With Genealogies and Arms (London, U.K.: Heraldry Today, 1972), page 209. Hereinafter cited as The New Extinct Peerage.
